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- 25 - technische universität dortmund fakultät für informatik P.Marwedel, Informatik 12, 2012 TU Dortmund Aliasing (2) Reconstruction impossible, if not sampling frequently enough How frequently do we have to sample? Nyquist criterion (sampling theory): Aliasing can be avoided if we restrict the frequencies of the incoming signal to less than half of the sampling rate. p s < ½ p N where p N is the period of the fastest sine wave or f s > 2 f N where f N is the frequency of the fastest sine wave f N is called the Nyquist frequency, f s is the sampling rate. See e.g. [Oppenheim/Schafer, 2009]